Fetal tachyarrhythmia is unfeigned in most cases and occurs in about 1–3% of the total number of pregnancies. Most of it's kinds are ectopic intraatrial reductions. FA is usually diagnosed during the routine, starting from 18 weeks of gestation, ultrasound assessment of the fetal heart rate. Approximately 10% of fetuses with rhythm disorders are at high risk of sudden death. Supraventricular tachycardia and atrial fibrillation are the most common causes of sudden death, the same is observed for bradyarrhythmias: manifest sinus bradycardia (hypoxic genesis) and expressed AV-blockade. The examination of all fetuses with arrhythmia was strongly recommended in cases of intrauterine cardiac arrest or death of the fetus in families. Arrhythmias which have been revealed during scheduled prenatal examination of the fetuses are in need of expert echocardiography assessment to determine the extent of possible pre- and postnatal risk of sudden death and the paril of arrhythmogenic cardiomyopathy formation. In case of identified life-threatening arrhythmia in fetus the pharmacological therapy, which greatly affects the favorable outcome is strongly recommended. It should be based on hemodynamic of pregnant and aimed to prevent the development of decompensation or arrhythmogenic cardiomyopathy.